User interface for segmented neurostimulation leads

ABSTRACT

An external control device for use with a neurostimulation system having a plurality of electrodes capable of conveying an electrical stimulation field into tissue in which the electrodes are implanted is provided. The external control device comprises a user interface having one or more control elements, a processor configured for generating stimulation parameters designed to modify the electrical stimulation field relative to one or more neurostimulation lead carrying the electrodes. The external control device further comprises output circuitry configured for transmitting the stimulation parameters to the neurostimulation system.

RELATED APPLICATION DATA

The present application is a continuation of U.S. patent applicationSer. No. 15/208,413 filed Jul. 12, 2016, which is a divisional of U.S.application Ser. No. 13/212,063 filed Aug. 17, 2011, which issued asU.S. Pat. No. 9,411,935, and which claims the benefit under 35 U.S.C. §119 to U.S. provisional patent application Ser. No. 61/374,879, filedAug. 18, 2010. The foregoing applications are hereby incorporated byreference into the present application in their entirety.

FIELD OF THE INVENTION

The present invention relates to tissue stimulation systems, and moreparticularly, to user interfaces and methods for controlling thedistribution of electrical current on segmented neurostimulation leads.

BACKGROUND OF THE INVENTION

Implantable neurostimulation systems have proven therapeutic in a widevariety of diseases and disorders. Pacemakers and Implantable CardiacDefibrillators (ICDs) have proven highly effective in the treatment of anumber of cardiac conditions (e.g., arrhythmias). Spinal CordStimulation (SCS) systems have long been accepted as a therapeuticmodality for the treatment of chronic pain syndromes, and theapplication of tissue stimulation has begun to expand to additionalapplications, such as angina pectoris and incontinence. Further, inrecent investigations, Peripheral Nerve Stimulation (PNS) systems havedemonstrated efficacy in the treatment of chronic pain syndromes andincontinence, and a number of additional applications are currentlyunder investigation. More pertinent to the present inventions describedherein, Deep Brain Stimulation (DBS) has been applied therapeuticallyfor well over a decade for the treatment of neurological disorders,including Parkinson's Disease, essential tremor, dystonia, and epilepsy,to name but a few. Further details discussing the treatment of diseasesusing DBS are disclosed in U.S. Pat. Nos. 6,845,267, 6,845,267, and6,950,707, which are expressly incorporated herein by reference.

Each of these implantable neurostimulation systems typically includesone or more electrode carrying stimulation leads, which are implanted atthe desired stimulation site, and a neurostimulator implanted remotelyfrom the stimulation site, but coupled either directly to theneurostimulation lead(s) or indirectly to the neurostimulation lead(s)via a lead extension. The neurostimulation system may further comprise ahandheld external control device to remotely instruct theneurostimulator to generate electrical stimulation pulses in accordancewith selected stimulation parameters. Typically, the stimulationparameters programmed into the neurostimulator can be adjusted bymanipulating controls on the external control device to modify theelectrical stimulation provided by the neurostimulator system to thepatient.

Thus, in accordance with the stimulation parameters programmed by theexternal control device, electrical pulses can be delivered from theneurostimulator to the stimulation electrode(s) to stimulate or activatea volume of tissue in accordance with a set of stimulation parametersand provide the desired efficacious therapy to the patient. The beststimulus parameter set will typically be one that delivers stimulationenergy to the volume of tissue that must be stimulated in order toprovide the therapeutic benefit (e.g., treatment of movement disorders),while minimizing the volume of non-target tissue that is stimulated. Atypical stimulation parameter set may include the electrodes that areacting as anodes or cathodes, as well as the amplitude, duration, andrate of the stimulation pulses.

Significantly, non-optimal electrode placement and stimulation parameterselections may result in excessive energy consumption due to stimulationthat is set at too high an amplitude, too wide a pulse duration, or toofast a frequency; inadequate or marginalized treatment due tostimulation that is set at too low an amplitude, too narrow a pulseduration, or too slow a frequency; or stimulation of neighboring cellpopulations that may result in undesirable side effects.

For example, bilateral DBS of the subthalamic nucleus has been proven toprovide effective therapy for improving the major motor signs ofadvanced Parkinson's disease, and although the bilateral stimulation ofthe subthalamic nucleus is considered safe, an emerging concern is thepotential negative consequences that it may have on cognitivefunctioning and overall quality of life (see A. M. M. Frankemolle, etal., Reversing Cognitive-Motor Impairments in Parkinson's DiseasePatients Using a Computational Modelling Approach to Deep BrainStimulation Programming, Brain 2010; pp. 1-16). In large part, thisphenomenon is due to the small size of the subthalamic nucleus. Evenwith the electrodes are located predominately within the sensorimotorterritory, the electrical field generated by DBS is non-discriminatelyapplied to all neural elements surrounding the electrodes, therebyresulting in the spread of current to neural elements affectingcognition. As a result, diminished cognitive function during stimulationof the subthalamic nucleus may occur do to non-selective activation ofnon-motor pathways within or around the subthalamic nucleus.

The large number of electrodes available, combined with the ability togenerate a variety of complex stimulation pulses, presents a hugeselection of stimulation parameter sets to the clinician or patient. Inthe context of DBS, neurostimulation leads with a complex arrangement ofelectrodes that not only are distributed axially along the leads, butare also distributed circumferentially around the neurostimulation leadsas segmented electrodes, can be used.

To facilitate such selection, the clinician generally programs theexternal control device, and if applicable the neurostimulator, througha computerized programming system. This programming system can be aself-contained hardware/software system, or can be defined predominantlyby software running on a standard personal computer (PC). The PC orcustom hardware may actively control the characteristics of theelectrical stimulation generated by the neurostimulator to allow theoptimum stimulation parameters to be determined based on patientfeedback and to subsequently program the external control device withthe optimum stimulation parameters.

When electrical leads are implanted within the patient, the computerizedprogramming system may be used to instruct the neurostimulator to applyelectrical stimulation to test placement of the leads and/or electrodes,thereby assuring that the leads and/or electrodes are implanted ineffective locations within the patient. Once the leads are correctlypositioned, a fitting procedure, which may be referred to as anavigation session, may be performed using the computerized programmingsystem to program the external control device, and if applicable theneurostimulator, with a set of stimulation parameters that bestaddresses the neurological disorder(s).

As physicians and clinicians become more comfortable with implantingneurostimulation systems and time in the operating room decreases,post-implant programming sessions are becoming a larger portion ofprocess. Furthermore, because the body tends to adapt to the specificstimulation parameters currently programmed into a neurostimulationsystem, or the full effects of stimulation are not manifest in a shortperiod of time (i.e., not observed within a programming session),follow-up programming procedures are often needed. For example, thebrain is dynamic (e.g., due to disease progression, motor re-learning,or other changes), and a program (i.e., a set of stimulation parameters)that is useful for a period of time may not maintain its effectivenessand/or the expectations of the patient may increase. Further, physicianstypically treat the patient with stimulation and medication, and properamounts of each are required for optimal therapy. Thus, after the DBSsystem has been implanted and fitted, the patient may have to scheduleanother visit to the physician in order to adjust the stimulationparameters of the DBS system if the treatment provided by the implantedDBS system is no longer effective or otherwise is not therapeutically oroperationally optimum due to, e.g., disease progression, motorre-learning, or other changes. Clinical estimates suggest that 18-36hours per patient are necessary to program and assess DBS patients withcurrent techniques (see Hunka K., et al., Nursing Time to Program andAssess Deep Brain Stimulators in Movement Disorder Patients, J. NeursciNurs. 37: 204-10).

There, thus, remains a need for a user interface that more efficientlyallows the programming of neurostimulation systems that utilizeneurostimulation leads with complex electrode arrangements.

SUMMARY OF THE INVENTION

The present inventions are directed to external control device (e.g., aclinician's programmer) for use with a neurostimulation system having aplurality of electrodes (which may be carried by one or moreneurostimulation leads) capable of conveying an electrical stimulationfield into tissue in which the electrodes are implanted is provided. Theexternal control device comprises a user interface having one or morecontrol elements, a processor configured for generating stimulationparameters designed to modify the electrical stimulation field relativeto the neurostimulation lead(s). In the case of a singleneurostimulation lead, the set stimulation parameter set is designed tomodify the electrical stimulation field relative to the axis of thesingle neurostimulation lead. The external control device furthercomprises output circuitry (e.g., telemetry circuitry) configured fortransmitting the stimulation parameters to the neurostimulation system.The user interface may further include a display screen, in which case,the control element(s) may take the form of icons on the display screen.The external control device may further comprise a housing containingthe user interface, processor, and output circuitry.

In accordance with one aspect of the present inventions, the userinterface includes a mode selection control element and an electricalstimulation field modification control element, and the processor isconfigured for selectively placing the electrical stimulation fieldmodification control element between an electrical stimulation fielddisplacement mode and an electrical stimulation field shaping mode whenthe mode selection control element is actuated. The processor is furtherconfigured for generating a first set of stimulation parameters designedto displace a locus of the electrical stimulation field when theelectrical stimulation field modification control element is actuated inthe electrical stimulation field displacement mode, and for generating asecond set of stimulation parameters designed to shape the electricalstimulation field about its locus when the electrical stimulation fieldmodification control element is actuated in the electrical stimulationfield shaping mode.

In one embodiment, the electrodes are arranged axially along one or moreneurostimulation leads, in which case, the first set of stimulationparameters may be designed to displace the electrical stimulation fieldalong the neurostimulation lead(s), and the second set of stimulationparameters may be designed to expand or contract the electricalstimulation field along the neurostimulation lead(s). In anotherembodiment, the electrodes are arranged circumferentially about the oneor more neurostimulation leads, in which case, the first set ofstimulation parameters may be designed to displace the electricalstimulation field about the neurostimulation lead(s), and the second setof stimulation parameters may be designed to expand or contract theelectrical stimulation field about the neurostimulation lead(s).

In accordance with a second aspect of the present inventions, the userinterface includes a circumferential modification control elementconfigured for being actuated (e.g., a rotational control elementconfigured for being rotated about a point), and the processor isconfigured for generating a set of stimulation parameters designed tocircumferentially displace a locus of the electrical stimulation fieldabout the neurostimulation lead(s) when the rotational control elementis rotated about the point.

In an optional embodiment, the user interface includes a markerassociated with the rotational control element. The marker indicates thecircumferential position of the locus of the electrical stimulationfield. In another optional embodiment, the user interface includes aradial modification control element, and the processor is furtherconfigured for generating another set of stimulation parameters designedto radially displace the locus of the electrical stimulation field whenthe radial modification control element is actuated. The radialmodification control element may be located on the rotational controlelement, in which case the radial modification control element may beconfigured for being radially displaced toward and away from the pointof the rotational control element.

In accordance with a third aspect of the present invention, the userinterface includes a circumferential modification control elementconfigured for being continually (e.g., continuously or repeatedly)actuated, and the processor is configured for generating sets ofstimulation parameters designed to circumferentially displace a locus ofthe electrical stimulation field about the neurostimulation lead(s) in afirst rotational direction at respective different angular positions asthe circumferential modification control element is continuallyactuated. The user interface may further include another circumferentialmodification control element configured for being continually actuated,in which case, the processor may be configured for generating other setsof stimulation parameters designed to circumferentially displace thelocus of the electrical stimulation field about the neurostimulationlead(s) in a second rotational direction opposite to the firstrotational direction at respective different angular positions as theother circumferential modification control element is continuallyactuated. In an optional embodiment, the user interface includes aradial modification control element, the processor is configured forgenerating another set of stimulation parameters designed to radiallyexpand or contract the electrical stimulation field when the radialmodification control element is actuated, and the output circuitry isconfigured for transmitting the other set of stimulation parameters tothe neurostimulation system.

In accordance with a fourth aspect of the present inventions, the userinterface includes a display screen (e.g., a touch screen) configuredfor displaying three-dimensional graphical renderings and a plurality oficonic control elements graphically linked to the three-dimensionalrenderings of the electrodes. The processor is configured for generatingstimulation parameters designed to modify the electrical stimulationfield when one of the iconic control elements is actuated. In oneembodiment, the stimulation parameters define an amplitude of electricalcurrent flowing through the electrode corresponding to the graphicalrendering of the electrode to which the actuated iconic control elementis graphically linked.

In another embodiment, the processor is configured for estimating avolume of tissue activation based on the generated stimulationparameters, and the display screen is configured for displaying ananatomical structure and the volume of tissue activation separately fromthe three-dimensional graphical renderings of the electrodes. In thiscase, the user interface includes a lead displacement control elementconfigured for being actuated, and the processor is configured forsynchronously displacing (e.g., axially and/or circumferentially) boththe three-dimensional graphical rendering of the electrodes and thevolume of tissue activation relative to the anatomical structure inresponse to the actuation of the lead displacement control element. Thedisplay screen may also be configured for displaying a three-dimensionalgraphical rendering of the neurostimulation lead with the volume oftissue activation and anatomical structure, and the processor isconfigured for synchronously displacing the three-dimensional graphicalrendering of the electrodes and the volume of tissue activation andgraphical rendering of the neurostimulation lead relative to theanatomical structure in response to the actuation of the leaddisplacement control element. The anatomical structure may be displayedin one of an axial view, a coronal view, and a sagittal view. In thiscase, the user interface may further include another control elementconfigured for being actuated, and the processor may be configured forselecting one of the axial view, coronal view, and sagittal view inresponse to the actuation of the other control element.

Other and further aspects and features of the invention will be evidentfrom reading the following detailed description of the preferredembodiments, which are intended to illustrate, not limit, the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of preferred embodimentsof the present invention, in which similar elements are referred to bycommon reference numerals. In order to better appreciate how theabove-recited and other advantages and objects of the present inventionsare obtained, a more particular description of the present inventionsbriefly described above will be rendered by reference to specificembodiments thereof, which are illustrated in the accompanying drawings.Understanding that these drawings depict only typical embodiments of theinvention and are not therefore to be considered limiting of its scope,the invention will be described and explained with additionalspecificity and detail through the use of the accompanying drawings inwhich:

FIG. 1 is a plan view of a Deep Brain Stimulation (DBS) systemconstructed in accordance with one embodiment of the present inventions;

FIG. 2 is a profile view of an implantable pulse generator (IPG) andneurostimulation leads used in the DBS system of FIG. 1;

FIG. 3 is a cross-sectional view of a neurostimulation lead used in theDBS system of FIG. 1;

FIG. 4 is a cross-sectional view of a patient's head showing theimplantation of stimulation leads and an IPG of the DBS system of FIG.1;

FIG. 5 is front view of a remote control (RC) used in the DBS system ofFIG. 1;

FIG. 6 is a block diagram of the internal components of the RC of FIG.5;

FIG. 7 is a block diagram of the internal components of a clinician'sprogrammer (CP) used in the DBS system of FIG. 1;

FIGS. 8A-8G are views showing activation of the electrodes to axially,circumferentially, and radially displace the locus of the electricalstimulation field relative to the neurostimulation lead;

FIGS. 9A-9D are views showing activation of the electrodes to axiallyand circumferentially expand/contract the electrical stimulation field;

FIG. 10 is a plan view of a user interface of the CP of FIG. 7 forprogramming the IPG of FIG. 2;

FIGS. 11A-11C are plan views illustrating alternative circumferentialmodification control elements that can be used in the user interface ofFIG. 10;

FIGS. 12A-12E are plan views illustrating rotational control elementsthat can be used in the user interface of FIG. 10;

FIG. 13 is a perspective view of an alternative three-dimensionalrendering of electrodes and control elements graphically associated withthe electrode renderings that can be used with the user interface ofFIG. 10;

FIG. 14 is a perspective view of a brain that can be displayed in anyone of a selected axial, coronal, or sagittal view generated by the userinterface of FIG. 10 to analyze a volume of activation.

DETAILED DESCRIPTION OF THE EMBODIMENTS

At the outset, it is noted that the present invention may be used withan implantable pulse generator (IPG), radio frequency (RF) transmitter,or similar neurostimulator, that may be used as a component of numerousdifferent types of stimulation systems. The description that followsrelates to a deep brain stimulation (DBS) system. However, it is to beunderstood that the while the invention lends itself well toapplications in DBS, the invention, in its broadest aspects, may not beso limited. Rather, the invention may be used with any type ofimplantable electrical circuitry used to stimulate tissue. For example,the present invention may be used as part of a pacemaker, adefibrillator, a cochlear stimulator, a retinal stimulator, a stimulatorconfigured to produce coordinated limb movement, a cortical stimulator,a spinal cord stimulator, peripheral nerve stimulator, microstimulator,or in any other neural stimulator configured to treat urinaryincontinence, sleep apnea, shoulder sublaxation, headache, etc.

Turning first to FIG. 1, an exemplary DBS neurostimulation system 10generally includes at least one implantable stimulation lead 12 (in thiscase, two), a neurostimulator in the form of an implantable pulsegenerator (IPG) 14, an external remote controller RC 16, a clinician'sprogrammer (CP) 18, an External Trial Stimulator (electrodes ETS) 20,and an external charger 22.

The IPG 14 is physically connected via one or more percutaneous leadextensions 24 to the neurostimulation leads 12, which carry a pluralityof electrodes 26 arranged in an array. In the illustrated embodiment,the neurostimulation leads 12 are percutaneous leads, and to this end,the electrodes 26 may be arranged in-line along the neurostimulationleads 12. In alternative embodiments, the electrodes 26 may be arrangedin a two-dimensional pattern on a single paddle lead. As will bedescribed in further detail below, the IPG 14 includes pulse generationcircuitry that delivers electrical stimulation energy in the form of apulsed electrical waveform (i.e., a temporal series of electricalpulses) to the electrode array 26 in accordance with a set ofstimulation parameters.

The ETS 20 may also be physically connected via the percutaneous leadextensions 28 and external cable 30 to the neurostimulation leads 12.The ETS 20, which has similar pulse generation circuitry as the IPG 14,also delivers electrical stimulation energy in the form of a pulseelectrical waveform to the electrode array 26 accordance with a set ofstimulation parameters. The major difference between the ETS 20 and theIPG 14 is that the ETS 20 is a non-implantable device that is used on atrial basis after the neurostimulation leads 12 have been implanted andprior to implantation of the IPG 14, to test the responsiveness of thestimulation that is to be provided.

The RC 16 may be used to telemetrically control the ETS 20 via abi-directional RF communications link 32. Once the IPG 14 andstimulation leads 12 are implanted, the RC 16 may be used totelemetrically control the IPG 14 via a bi-directional RF communicationslink 34. Such control allows the IPG 14 to be turned on or off and to beprogrammed with different stimulation parameter sets. The IPG 14 mayalso be operated to modify the programmed stimulation parameters toactively control the characteristics of the electrical stimulationenergy output by the IPG 14. As will be described in further detailbelow, the CP 18 provides clinician detailed stimulation parameters forprogramming the IPG 14 and ETS 20 in the operating room and in follow-upsessions.

The CP 18 may perform this function by indirectly communicating with theIPG 14 or ETS 20, through the RC 16, via an IR communications link 36.Alternatively, the CP 18 may directly communicate with the IPG 14 or ETS20 via an RF communications link (not shown). The clinician detailedstimulation parameters provided by the CP 18 are also used to programthe RC 16, so that the stimulation parameters can be subsequentlymodified by operation of the RC 16 in a stand-alone mode (i.e., withoutthe assistance of the CP 18).

The external charger 22 is a portable device used to transcutaneouslycharge the IPG 14 via an inductive link 38. For purposes of brevity, thedetails of the external charger 22 will not be described herein. Detailsof exemplary embodiments of external chargers are disclosed in U.S. Pat.No. 6,895,280, which has been previously incorporated herein byreference. Once the IPG 14 has been programmed, and its power source hasbeen charged by the external charger 22 or otherwise replenished, theIPG 14 may function as programmed without the RC 16 or CP 18 beingpresent.

Referring to FIG. 2, the IPG 14 comprises an outer case 40 for housingthe electronic and other components (described in further detail below),and a connector 42 to which the proximal end of the neurostimulationlead 12 mates in a manner that electrically couples the electrodes 26 tothe internal electronics (described in further detail below) within theouter case 40. The outer case 40 is composed of an electricallyconductive, biocompatible material, such as titanium, and forms ahermetically sealed compartment wherein the internal electronics areprotected from the body tissue and fluids. In some cases, the outer case40 may serve as an electrode.

Each of the neurostimulation leads 12 comprises an elongated cylindricallead body 43, and the electrodes 26 take the form of segmentedelectrodes that are circumferentially and axially disposed about thelead body 43. By way of non-limiting example, and with further referenceto FIG. 3, each neurostimulation lead 12 may carry sixteen electrodes,arranged as four rings of electrodes (the first ring consisting ofelectrodes E1-E4; the second ring consisting of electrodes E5-E8; thethird ring consisting of electrodes E9-E12; and the fourth ringconsisting of E13-E16) or four axial columns of electrodes (the firstcolumn consisting of electrodes E1, E5, E9, and E13; the second columnconsisting of electrodes E2, E6, E10, and E14; the third columnconsisting of electrodes E3, E7, E11, and E15; and the fourth columnconsisting of electrodes E4, E8, E12, and E16). The actual number andshape of leads and electrodes will, of course, vary according to theintended application. Further details describing the construction andmethod of manufacturing percutaneous stimulation leads are disclosed inU.S. patent application Ser. No. 11/689,918, entitled “Lead Assembly andMethod of Making Same,” and U.S. patent application Ser. No. 11/565,547,entitled “Cylindrical Multi-Contact Electrode Lead for NeuralStimulation and Method of Making Same,” the disclosures of which areexpressly incorporated herein by reference.

As will be described in further detail below, the IPG 14 includes abattery and pulse generation circuitry that delivers the electricalstimulation energy in the form of a pulsed electrical waveform to theelectrode array 26 in accordance with a set of stimulation parametersprogrammed into the IPG 14. Such stimulation parameters may compriseelectrode combinations, which define the electrodes that are activatedas anodes (positive), cathodes (negative), and turned off (zero),percentage of stimulation energy assigned to each electrode(fractionalized electrode configurations), and electrical pulseparameters, which define the pulse amplitude (measured in milliamps orvolts depending on whether the IPG 14 supplies constant current orconstant voltage to the electrode array 26), pulse duration (measured inmicroseconds), pulse rate (measured in pulses per second), and burstrate (measured as the stimulation on duration X and stimulation offduration Y).

Electrical stimulation will occur between two (or more) activatedelectrodes, one of which may be the IPG case. Simulation energy may betransmitted to the tissue in a monopolar or multipolar (e.g., bipolar,tripolar, etc.) fashion. Monopolar stimulation occurs when a selectedone of the lead electrodes 26 is activated along with the case of theIPG 14, so that stimulation energy is transmitted between the selectedelectrode 26 and case. Bipolar stimulation occurs when two of the leadelectrodes 26 are activated as anode and cathode, so that stimulationenergy is transmitted between the selected electrodes 26. Tripolarstimulation occurs when three of the lead electrodes 26 are activated,two as anodes and the remaining one as a cathode, or two as cathodes andthe remaining one as an anode.

In the illustrated embodiment, IPG 14 can individually control themagnitude of electrical current flowing through each of the electrodes.In this case, it is preferred to have a current generator, whereinindividual current-regulated amplitudes from independent current sourcesfor each electrode may be selectively generated. Although this system isoptimal to take advantage of the invention, other stimulators that maybe used with the invention include stimulators having voltage regulatedoutputs. While individually programmable electrode amplitudes areoptimal to achieve fine control, a single output source switched acrosselectrodes may also be used, although with less fine control inprogramming. Mixed current and voltage regulated devices may also beused with the invention. Further details discussing the detailedstructure and function of IPGs are described more fully in U.S. Pat.Nos. 6,516,227 and 6,993,384, which are expressly incorporated herein byreference.

As shown in FIG. 4, two percutaneous neurostimulation leads 12 areintroduced through a burr hole 46 (or alternatively, two respective burrholes) formed in the cranium 48 of a patient 44, and introduced into theparenchyma of the brain 49 of the patient 44 in a conventional manner,such that the electrodes 26 are adjacent a target tissue region, thestimulation of which will treat the dysfunction (e.g., the ventrolateralthalamus, internal segment of globus pallidus, substantia nigra parsreticulate, subthalamic nucleus, or external segment of globuspallidus). Thus, stimulation energy can be conveyed from the electrodes26 to the target tissue region to change the status of the dysfunction.Due to the lack of space near the location where the neurostimulationleads 12 exit the burr hole 46, the IPG 14 is generally implanted in asurgically-made pocket either in the chest, or in the abdomen. The IPG14 may, of course, also be implanted in other locations of the patient'sbody. The lead extension(s) 24 facilitates locating the IPG 14 away fromthe exit point of the neurostimulation leads 12.

Referring now to FIG. 5, one exemplary embodiment of an RC 16 will nowbe described. As previously discussed, the RC 16 is capable ofcommunicating with the IPG 14, CP 18, or ETS 20. The RC 16 comprises acasing 50, which houses internal componentry (including a printedcircuit board (PCB)), and a lighted display screen 52 and button pad 54carried by the exterior of the casing 50. In the illustrated embodiment,the display screen 52 is a lighted flat panel display screen, and thebutton pad 54 comprises a membrane switch with metal domes positionedover a flex circuit, and a keypad connector connected directly to a PCB.In an optional embodiment, the display screen 52 has touchscreencapabilities. The button pad 54 includes a multitude of buttons 56, 58,60, and 62, which allow the IPG 14 to be turned ON and OFF, provide forthe adjustment or setting of stimulation parameters within the IPG 14,and provide for selection between screens.

In the illustrated embodiment, the button 56 serves as an ON/OFF buttonthat can be actuated to turn the IPG 14 ON and OFF. The button 58 servesas a select button that allows the RC 16 to switch between screendisplays and/or parameters. The buttons 60 and 62 serve as up/downbuttons that can actuated to increment or decrement any of stimulationparameters of the pulse generated by the IPG 14, including pulseamplitude, pulse width, and pulse rate. For example, the selectionbutton 58 can be actuated to place the RC 16 in an “Pulse AmplitudeAdjustment Mode,” during which the pulse amplitude can be adjusted viathe up/down buttons 60, 62, a “Pulse Width Adjustment Mode,” duringwhich the pulse width can be adjusted via the up/down buttons 60, 62,and a “Pulse Rate Adjustment Mode,” during which the pulse rate can beadjusted via the up/down buttons 60, 62. Alternatively, dedicatedup/down buttons can be provided for each stimulation parameter. Ratherthan using up/down buttons, any other type of actuator, such as a dial,slider bar, or keypad, can be used to increment or decrement thestimulation parameters. Further details of the functionality andinternal componentry of the RC 16 are disclosed in U.S. Pat. No.6,895,280, which has previously been incorporated herein by reference.

Referring to FIG. 6, the internal components of an exemplary RC 16 willnow be described. The RC 16 generally includes a processor 64 (e.g., amicrocontroller), memory 66 that stores an operating program forexecution by the processor 64, as well as stimulation parameter sets ina look-up table (described below), input/output circuitry, and inparticular, telemetry circuitry 68 for outputting stimulation parametersto the IPG 14 and receiving status information from the IPG 14, andinput/output circuitry 70 for receiving stimulation control signals fromthe button pad 54 and transmitting status information to the displayscreen 52 (shown in FIG. 5). As well as controlling other functions ofthe RC 16, which will not be described herein for purposes of brevity,the processor 64 generates new stimulation parameter sets in response tothe user operation of the button pad 54. These new stimulation parametersets would then be transmitted to the IPG 14 (or ETS 20) via thetelemetry circuitry 68. Further details of the functionality andinternal componentry of the RC 16 are disclosed in U.S. Pat. No.6,895,280, which has previously been incorporated herein by reference.

As briefly discussed above, the CP 18 greatly simplifies the programmingof multiple electrode combinations, allowing the physician or clinicianto readily determine the desired stimulation parameters to be programmedinto the IPG 14, as well as the RC 16. Thus, modification of thestimulation parameters in the programmable memory of the IPG 14 afterimplantation is performed by a clinician using the CP 18, which candirectly communicate with the IPG 14 or indirectly communicate with theIPG 14 via the RC 16. That is, the CP 18 can be used by the physician orclinician to modify operating parameters of the electrode array 26 inthe brain.

The overall appearance of the CP 18 is that of a laptop personalcomputer (PC), and in fact, may be implanted using a PC that has beenappropriately configured to include a directional-programming device andprogrammed to perform the functions described herein. Alternatively, theCP 18 may take the form of a mini-computer, personal digital assistant(PDA), etc., or even a remote control (RC) with expanded functionality.Thus, the programming methodologies can be performed by executingsoftware instructions contained within the CP 18. Alternatively, suchprogramming methodologies can be performed using firmware or hardware.In any event, the CP 18 may actively control the characteristics of theelectrical stimulation generated by the IPG 14 (or ETS 20) to allow theoptimum stimulation parameters to be determined based on patientresponse and feedback and for subsequently programming the IPG 14 (orETS 20) with the optimum stimulation parameters.

To allow the user to perform these functions, the CP 18 includes a mouse72, a keyboard 74, and a display screen 76 housed in a case 78. In theillustrated embodiment, the display screen 76 is a conventional screen.It is to be understood that in addition to, or in lieu of, the mouse 72,other directional programming devices may be used, such as a trackball,touchpad, or joystick, can be used. Alternatively, instead of beingconventional, the display screen 76 may be a digitizer screen, such astouchscreen) (not shown), may be used in conjunction with an active orpassive digitizer stylus/finger touch. As shown in FIG. 7, the CP 18generally includes a processor 80 (e.g., a central processor unit (CPU))and memory 82 that stores a stimulation programming package 84, whichcan be executed by the processor 80 to allow the user to program the IPG14, and RC 16. The CP 18 further includes output circuitry 86 (e.g., viathe telemetry circuitry of the RC 16) for downloading stimulationparameters to the IPG 14 and RC 16 and for uploading stimulationparameters already stored in the memory 66 of the RC 16, via thetelemetry circuitry 68 of the RC 16.

Execution of the programming package 84 by the processor 80 provides amultitude of display screens (not shown) that can be navigated throughvia use of the mouse 72. These display screens allow the clinician to,among other functions, to select or enter patient profile information(e.g., name, birth date, patient identification, physician, diagnosis,and address), enter procedure information (e.g., programming/follow-up,implant trial system, implant IPG, implant IPG and lead(s), replace IPG,replace IPG and leads, replace or revise leads, explant, etc.), generatea pain map of the patient, define the configuration and orientation ofthe leads, initiate and control the electrical stimulation energy outputby the leads 12, and select and program the IPG 14 with stimulationparameters in both a surgical setting and a clinical setting. Furtherdetails discussing the above-described CP functions are disclosed inU.S. patent application Ser. No. 12/501,282, entitled “System and Methodfor Converting Tissue Stimulation Programs in a Format Usable by anElectrical Current Steering Navigator,” and U.S. patent application Ser.No. 12/614,942, entitled “System and Method for Determining AppropriateSteering Tables for Distributing Stimulation Energy Among MultipleNeurostimulation Electrodes,” which are expressly incorporated herein byreference.

Most pertinent to the present inventions, execution of the programmingpackage 84 provides a more intuitive user interface that allows theelectrical stimulation field conveyed by selected ones of the electrodes26 to be modified, e.g., by axially, circumferentially, and/or radiallydisplacing the locus of the stimulation field circumferentially relativeto a single neurostimulation lead 12 or both neurostimulation leads 12,and axially and/or circumferentially expanding or contracting theelectrical stimulation field about its locus.

Before discussing the intuitive user interface in detail, it will beuseful to describe the various methods that can be used to modify theelectrical stimulation field conveyed by the electrodes 26. For purposesof simplicity, the electrodes 26 will be described as being operated ina monopolar fashion, with one or more of the electrodes 26 arranged as astimulating cathode (“−” polarity) and the case 40 arranged as the anode(“+” polarity), although the same principles described herein can beapplied to the electrodes 26 when operated in a bipolar fashion.

In one method, different electrode combinations can be discretelyselected to displace the locus of the electrical stimulation field fromone location to another location within the electrode array 12.

For example, with reference to FIGS. 8A and 8B, a first stimulatinggroup of electrodes 26 consisting of two electrodes in the second ringand respectively in the second and third columns (electrodes E6, E7) canbe activated as cathodes. This polarity and grouping causes electricalcurrent to flow from the case electrode to electrodes E6 and E7 in amonopolar fashion, which results in a locus of the electricalstimulation field positioned equally between these two electrodes.

As shown in FIG. 8C, a second stimulating group of electrodes 26consisting of two electrodes in the third ring (electrodes E10, E11) canbe activated as cathodes. This polarity and grouping causes electricalcurrent to flow from the case electrode to electrodes E10 and E11 in amonopolar fashion, which results in a locus of the electricalstimulation field positioned equally between these two electrodes. Thus,it can be appreciated from this that the locus of the electricalstimulation field can be axially displaced in the distal direction alongthe lead 12 by switching from the first stimulating group of electrodes(electrodes E6, E7) to the second stimulating group of electrodes(electrodes E10, E11), and can be axially displaced in the proximaldirection along the lead 12 by switching from the second stimulatinggroup of electrodes (electrodes E10, E11) to the first stimulating groupof electrodes (electrodes E6, E7).

As shown in FIG. 8D, a third stimulating group of electrodes 26consisting of an electrode in the first column (electrode E5) and anelectrode in the second column (electrode E6) can be activated ascathodes. This polarity and grouping causes electrical current to flowfrom the case electrode to electrodes E5 and E6 in a monopolar fashion,which results in a locus of the electrical stimulation field positionedequally between these two electrodes. Thus, it can be appreciated fromthis that the locus of the electrical stimulation field can becircumferentially displaced in the counterclockwise direction about thelead 12 by switching from the first stimulating group of electrodes(electrodes E6, E7) to the fourth stimulating group of electrodes(electrodes E5, E6), and can be circumferentially displaced in theclockwise direction about the lead 12 by switching from the thirdstimulating group of electrodes (electrodes E6, E7) to the firststimulating group of electrodes (electrodes E5, E6).

As shown in FIG. 8E, one or more electrodes 26 opposite the firststimulating group of electrodes 26, and in this case, electrodes E5 andE8, can be activated as an anode, and the amplitude of the currentflowing through the first stimulating group of electrodes (electrodesE6, E7) can be increased to displace the locus of the electricalstimulation field radially outward from the lead 12. Electrodes E5 andE8, can be inactivated, and the amplitude of the current flowing throughthe first stimulating group of electrodes (electrodes E6, E7) can bedecreased to displace the locus of the electrical stimulation fieldradially inward towards the lead 12.

Of course, other electrode combinations, including bipolar and tripolarcombinations, can be selected to electronically displace the locus ofthe electrical stimulation field.

In another method, rather than discretely selecting differentcombinations of electrodes, electrical current can be gradually“steered” or shifted between electrodes to displace the locus of theelectrical stimulation field.

For example, assuming that electrodes E6 and E7 are the only electrodesin the stimulating group, the locus of the electrical stimulation fieldcan be gradually displaced axially in the distal direction along thelead 12 by gradually including electrodes E10 and E11 in the stimulatingelectrode group and gradually excluding electrodes E6 and E7 from thestimulating electrode group. That is, the fractionalized cathodiccurrent flowing through each of electrodes E10 and E11 is incrementallyincreased from 0% to 50%, while the fractionalized cathodic currentflowing through each of electrodes E6 and E7 is incrementally decreasedfrom 50% to 0%. As a result, the electrical stimulation field graduallymoves from its initial position, as shown in FIG. 8A, to an axiallydisplaced position, as shown in FIG. 8C. One incremental step may be,e.g., where fractionalized cathodic current flowing through each ofelectrodes E10 and E11 is 15%, and the fractionalized cathodic currentflowing through each of electrodes E6 and E7 is 35%, in which case theelectrical stimulation field may be in an axially displaced position, asshown in FIG. 8F.

Assuming that electrodes E10 and E11 are now the only electrodes in thestimulating group, the locus of the electrical stimulation field can begradually displaced axially in the proximal direction along the lead 12by gradually including electrodes E6 and E7 in the stimulating electrodegroup and gradually excluding electrodes E10 and E11 from thestimulating electrode group. That is, the fractionalized cathodiccurrent flowing through each of electrodes E6 and E7 is incrementallyincreased from 0% to 50%, while the fractionalized cathodic currentflowing through each of electrodes E10 and E11 is incrementallydecreased from 50% to 0%. As a result, the electrical stimulation fieldgradually moves from the position shown in FIG. 8C to the axiallydisplaced position shown in FIG. 8A.

Assuming that electrodes E6 and E7 are the only electrodes in thestimulating group, the locus of the electrical stimulation field can begradually displaced circumferentially in the counterclockwise directionabout the lead 12 by gradually including electrode E5 in the stimulatingelectrode group and gradually excluding electrode E7 from thestimulating electrode group. That is, the fractionalized cathodiccurrent flowing through electrode E5 is incrementally increased from 0%to 50%, while the fractionalized cathodic current flowing throughelectrode E7 is incrementally decreased from 50% to 0%. As a result, theelectrical stimulation field gradually moves from the position shown inFIG. 8B to the circumferentially displaced position shown in FIG. 8D.One incremental step may be, e.g., where fractionalized cathodic currentflowing through electrode E6 remains 50%, the fractionalized cathodiccurrent flowing through electrode E7 is 15%, and the fractionalizedcathodic current flowing through electrode E5 is 35%, in which case theelectrical stimulation field may be in circumferentially displacedposition, as shown in FIG. 8G.

Assuming that electrodes E5 and E6 are now the only electrodes in thestimulating group, the locus of the electrical stimulation field can begradually displaced circumferentially in the clockwise direction aboutthe lead 12 by gradually including electrode E7 in the stimulatingelectrode group and gradually excluding electrode E5 from thestimulating electrode group. That is, the fractionalized cathodiccurrent flowing through electrode E7 is incrementally increased from 0%to 50%, while the fractionalized cathodic current flowing throughelectrode E5 is incrementally decreased from 50% to 0%. As a result, theelectrical stimulation field gradually moves from the position shown inFIG. 8D to the circumferentially displaced position shown in FIG. 8B.

In still another method, the locus of the electrical stimulation fieldis electronically displaced using multiple timing channels. Inparticular, the electrical energy can be conveyed between differentcombinations of electrodes in accordance with multiple timing channels;that is, a first stimulating electrode group can be used during a firsttiming channel, a second stimulating electrode group can be used duringa second timing channel, and so forth, and the groups may or may notoverlap. The magnitude of the electrical energy conveyed in accordancewith at least one of the multiple timing channels can be modified toeffectively displace the locus of the stimulation region.

For example, during a first timing channel, a first stimulating group ofelectrodes 26 consisting of two electrodes in the second ring(electrodes E6, E7) can be activated as cathodes. During a second timingchannel, a second stimulating group of electrodes 26 consisting of twoelectrodes in the third ring (electrodes E10, E11) can be activated ascathodes. This polarity and grouping causes electrical current to flowfrom the case electrode to electrodes E6 and E7 during the first timingchannel in a monopolar fashion, and from the case electrode toelectrodes E10 and E11 during the second timing channel in a monopolarfashion.

The first and second timing channels are simultaneously operatedtogether, such that the electrical pulses generated at electrodes E6 andE7 are interleaved between the electrical pulses generated at electrodesE10 and E11. If the amplitude of the current of the first timing channel(controlling E6 and E7) and the amplitude of the current of the secondtiming channel (controlling E10 and E11) are the same, the result iseffectively an overall region of stimulation region that encompassesboth the stimulation field as shown in FIG. 8A and the stimulation fieldas shown in FIG. 8C, with an overall center position between the E6/E7and E10/E11 contact pairs.

It can be appreciated from this that the magnitude of the electricalenergy at electrodes E6 and E7 during the first timing channel and/orthe electrical energy at electrodes E10 and E11 during the second timingchannel can be modified to gradually displace the locus of theelectrical stimulation field along the lead 12. For example, if thepulse amplitude and/or pulse duration of the electrical energy atelectrodes E10 and E11 during the second timing channel is increasedrelative to the pulse amplitude and/or pulse duration of the electricalenergy at electrodes E6 and E7 during the first timing channel, thelocus of the electrical stimulation field will be effectively displacedaxially in the distal direction closer to the position equidistantbetween electrodes E10) and E11. In contrast, if the pulse amplitudeand/or pulse duration of the electrical energy at electrodes E10 and E11during the second timing channel is decreased relative to the pulseamplitude and/or pulse duration of the electrical energy at electrodesE6 and E7 during the first timing channel, the locus of the electricalstimulation field will be effectively displaced axially in the proximaldirection closer to the position equidistant between electrodes E6 andE7. It is appreciated that if there is neural tissue that is affected byboth timing channels, the stimulation rate will be some composite of theeffects of the two timing channels in that tissue region.

As still another example, during a first timing channel, a firststimulating group of electrodes 26 consisting an electrode in the secondcolumn (electrode E6) and an electrode in the third column (electrodeE7) can be activated as cathodes. During a second timing channel, asecond stimulating group of electrodes 26 consisting an electrode in thefirst column (electrode E5) and an electrode in the second column(electrode E6) can be activated as cathodes. This polarity and groupingcauses electrical current to flow from the case electrode to electrodesE6 and E7 during the first timing channel in a monopolar fashion, andfrom the case electrode to electrodes E5 and E6 during the second timingchannel in a monopolar fashion.

The first and second timing channels are simultaneously operatedtogether, such that the electrical pulses generated at electrodes E6 andE7 are interleaved between the electrical pulses generated at electrodesE5 and E6. If the amplitude of the current of the first timing channel(controlling E6 and E7) and the amplitude of the current of the secondtiming channel (controlling E5 and E6) are the same, the result iseffectively an overall region of stimulation region that encompassesboth the stimulation field as shown in FIG. 8B and the stimulation fieldas shown in FIG. 8D, with an overall center position between the E6/E7and E5/E6 contact pairs.

It can be appreciated from this that the magnitude of the electricalenergy at electrodes E6 and E7 during the first timing channel and/orthe electrical energy at electrodes E5 and E6 during the second timingchannel can be modified to gradually circumferentially displace thelocus of the electrical stimulation field about the lead 12. Forexample, if the pulse amplitude and/or pulse duration of the electricalenergy at electrodes E5 and E6 during the second timing channel isincreased relative to the pulse amplitude and/or pulse duration of theelectrical energy at electrodes E6 and E7 during the first timingchannel, the locus of the electrical stimulation field will beeffectively displaced circumferentially in the counterclockwisedirection closer to the position equidistant between electrodes E5 andE6. If the pulse amplitude and/or pulse duration of the electricalenergy at electrodes E5 and E6 during the second timing channel isdecreased relative to the pulse amplitude and/or pulse duration of theelectrical energy at electrodes E6 and E7 during the first timingchannel, the locus of the electrical stimulation field will beeffectively displaced circumferentially in the clockwise directioncloser to the position equidistant between electrodes E6 and E7. Itshould also be noted that timing channels can stimulate multiple locithat are not spatially contiguous, and the changing the relativeamplitudes can change the amount of stimulated tissue at each of themultiple loci.

The electrical stimulation field may be modified in manners other thandisplacing its locus from one location to another location within theelectrode array 12. For example, the electrical stimulation field may bemodified by expanding or contacting the electrical stimulation fieldabout its locus.

In one method, different electrodes can be discretely selected in thesame manner discussed above with respect to the displacement of thelocus of the electrical stimulation field, with the exception that thesize of the electrical stimulation field is expanded or contracted.

For example, as shown in FIG. 9A and 9B, a first stimulating group ofelectrodes 26 consisting of an electrode in the second ring and thesecond column (electrode E6) can be activated as a cathode. Thispolarity and grouping causes electrical current to flow from the caseelectrode to electrode E6 in a monopolar fashion, which results in anelectrical stimulation field adjacent this electrode.

As shown in FIG. 9C, a second stimulating group of electrodes 26consisting of three electrodes in the second column (electrodes E2, E6,E10) can be activated as cathodes. This polarity and grouping causeselectrical current to flow from the case electrode to electrodes E2, E6,and E10 in a monopolar fashion, which results in an electricalstimulation field that spans these three electrodes. Thus, it can beappreciated from this that the electrical stimulation field can beaxially expanded along the lead 12 by switching from the firststimulating group of electrodes (electrodes E6) to the secondstimulating group of electrodes (electrodes E2, E6, E10). In contrast,the electrical stimulation field can be axially contracted along thelead 12 by switching from the second stimulating group of electrodes(electrode E2, E6, E10) to the first group of stimulating electrodes(electrode E6).

As shown in FIG. 9D, a third stimulating group of electrodes 26consisting of three electrodes in the second ring (electrodes E5, E6,E7) can be activated as cathodes. This polarity and grouping causeselectrical current to flow from the case electrode to electrodes E5, E6,and E7 in a monopolar fashion, which results in an electricalstimulation field that spans these three electrodes. Thus, it can beappreciated from this that the electrical stimulation field can becircumferentially expanded about the lead 12 by switching from the firststimulating group of electrodes (electrode E6) to the third stimulatinggroup of electrodes (electrodes E5, E6, E7). In contrast, the electricalstimulation field can be circumferentially contracted about the lead 12by switching from the second stimulating group of electrodes (electrodesE5, E6, E7) to the first stimulating group of electrodes (E6).

Although the electrical stimulation field has been described as above asbeing expanded or contracted equally around its locus, it should benoted that the electrical stimulation field may be expanded orcontracted asymmetrically about the initial locus. For example, anelectrical stimulation field may be axially expanded or contracted indistal direction without being expanded or contracted in the proximaldirection, or the electrical stimulation field can be circumferentiallyexpanded or contracted in the counter-clockwise direction without beingexpanded or contracted in the clockwise direction

In another method, electrical current can be gradually “steered” orshifted between electrodes to expand and contract the electricalstimulation field in a similar manner described above with respect tothe displacement of the locus of the electrical stimulation field, withthe exception that the locus of the electrical stimulation field ismaintained, and instead the electrical stimulation field is expanded orcontracted.

For example, assuming that electrode E6 is the only electrode in thestimulating group, the electrical stimulation field can be graduallyexpanded axially along the lead 12 by gradually including electrodes E2and E10 in the stimulating electrode group. That is, the fractionalizedcathodic current flowing through each of electrodes E2 and E10 isincrementally increased from 0% to 33 ⅓%, while the fractionalizedcathodic current flowing through electrode E6 is incrementally decreasedfrom 100% to 33 ⅓%. As a result, the electrical stimulation fieldgradually expands from its footprint, as shown in FIG. 9A, to an axiallyexpanded footprint, as shown in FIG. 9C. Assuming that electrodes E2,E6, and E10 are now the only electrodes in the stimulating group, theelectrical stimulation field can be gradually contracted axially alongthe lead 12 by gradually excluding electrodes E2 and E10 from thestimulating electrode group. That is, the fractionalized cathodiccurrent flowing through each of electrodes E2 and E10 is incrementallydecreased from 33 ⅓% to 0%, while the fractionalized cathodic currentflowing through electrode E6 is incrementally increased from 33 ⅓% to100%. As a result, the electrical stimulation field gradually contractsfrom its footprint, as shown in FIG. 9C, to an axially contractedfootprint, as shown in FIG. 9A.

As another example, assuming that electrode E6 is the only electrode inthe stimulating group, the electrical stimulation field can be graduallyexpanded circumferentially about the lead 12 by gradually includingelectrodes E5 and E7 in the stimulating electrode group. That is, thefractionalized cathodic current flowing through each of electrodes E5and E7 is incrementally increased from 0% to 33 ⅓%, while thefractionalized cathodic current flowing through electrode E6 isincrementally decreased from 100% to 33 ⅓%. As a result, the electricalstimulation field gradually expands from its footprint, as shown in FIG.9B, to an axially expanded footprint, as shown in FIG. 9D. Assuming thatelectrodes E5, E6, and E7 are now the only electrodes in the stimulatinggroup, the electrical stimulation field can be gradually contractedcircumferentially about the lead 12 by gradually excluding electrodes E5and E7 from the stimulating electrode group. That is, the fractionalizedcathodic current flowing through each of electrodes E5 and E7 isincrementally decreased from 33 ⅓% to 0%, while the fractionalizedcathodic current flowing through electrode E6 is incrementally increasedfrom 33 ⅓% to 100%. As a result, the electrical stimulation fieldgradually contracts from its footprint, as shown in FIG. 9D, to anaxially contracted footprint, as shown in FIG. 9B.

In still another method, the electrical stimulation field can begradually expanded or contracted using multiple timing channels.

For example, during a first timing channel, a first stimulating group ofelectrodes 26 consisting of an electrode in the second ring (electrodeE6) can be activated as a cathode. During a second timing channel, asecond stimulating group of electrodes 26 consisting of three electrodesrespectively in the first, second and third rings (electrodes E2, E6,E10) can be activated as cathodes. This polarity and grouping causeselectrical current to flow from the case electrode to electrodes E6during the first timing channel in a monopolar fashion, and from thecase electrode to electrodes E2, E6, and E10 during the second timingchannel in a monopolar fashion.

The first and second timing channels are simultaneously operatedtogether, such that the electrical pulses generated at electrode E6 areinterleaved between the electrical pulses generated at electrodes E2,E6, and E10, effectively resulting in a single electrical stimulationfield that covers an area that spans only electrode E6 to an area thatspans electrodes E2, E6, and E10, although in any given instant of time,the electrical stimulation field will either span only electrode E6, asshown in FIG. 9A, or span electrodes E2, E6, and E10, as shown in FIG.9C.

It can be appreciated from this that the magnitude of the electricalenergy at electrodes E6 during the first timing channel and/or theelectrical energy at electrodes E2, E6, and E10 during the second timingchannel can be modified to gradually expand or contract the electricalstimulation field axially along the lead 12. For example, if the pulseamplitude and/or pulse duration of the electrical energy at electrodesE2, E6, and E10 during the second timing channel is increased relativeto the pulse amplitude and/or pulse duration of the electrical energy atelectrode E6 during the first timing channel, the electrical stimulationfield will be effectively axially expanded along the lead 12. Incontrast, if the pulse amplitude and/or pulse duration of the electricalenergy at electrodes E2, E6, and E10 during the second timing channel isdecreased relative to the pulse amplitude and/or pulse duration of theelectrical energy at electrode E6 during the first timing channel, theelectrical stimulation field will be effectively axially contractedalong the lead 12.

As another example, during a first timing channel, a first stimulatinggroup of electrodes 26 consisting of an electrode in the second column(electrode E6) can be activated as a cathode. During a second timingchannel, a second stimulating group of electrodes 26 consisting of threeelectrodes respectively in the first, second, and third columns(electrodes E5, E6, E7) can be activated as cathodes. This polarity andgrouping causes electrical current to flow from the case electrode toelectrodes E6 during the first timing channel in a monopolar fashion,and from the case electrode to electrodes E5, E6, and E7 during thesecond timing channel in a monopolar fashion.

The first and second timing channels are simultaneously operatedtogether, such that the electrical pulses generated at electrode E6 areinterleaved between the electrical pulses generated at electrodes E5,E6, and E7 effectively resulting in a single electrical stimulationfield that covers an area that spans only electrode E6 to an area thatspans electrodes E5, E6, and E7, although in any given instant of time,the electrical stimulation field will either span only electrode E6, asshown in FIG. 9B, or span electrodes E5, E6, and E7, as shown in FIG.9D.

It can be appreciated from this that the magnitude of the electricalenergy at electrodes E6 during the first timing channel and/or theelectrical energy at electrodes E2, E6, and E10 during the second timingchannel can be modified to gradually expand or contract the electricalstimulation field circumferentially about the lead 12. For example, ifthe pulse amplitude and/or pulse duration of the electrical energy atelectrodes E5, E6, and E7 during the second timing channel is increasedrelative to the pulse amplitude and/or pulse duration of the electricalenergy at electrode E6 during the first timing channel, the electricalstimulation field will be effectively circumferentially expanded aboutthe lead 12. In contrast, if the pulse amplitude and/or pulse durationof the electrical energy at electrodes E5, E6, and E7 during the secondtiming channel is decreased relative to the pulse amplitude and/or pulseduration of the electrical energy at electrode E6 during the firsttiming channel, the electrical stimulation field will be effectivelycircumferentially contracted about the lead 12.

It should be noted that although the modification of the electricalstimulation field has been described with respect to a single lead, theelectrical stimulation field can be modified relative to multiple leadsby assuming ideal poles and computationally determining the stimulationparameters necessary to emulate the ideal poles, as described in U.S.Provisional Application Ser. No. 61/257,753, entitled “System and Methodfor Mapping Arbitrary Electric Fields to Pre-existing Lead Electrodes,”which is incorporated herein by reference.

Returning now to the operation of the user interface of the CP 16, aprogramming screen 100 can be generated by the CP 16, as shown in FIG.10. The programming screen 100 allows a user to perform stimulationparameter testing.

The programming screen 100 further comprises a stimulation on/offcontrol 102 that can be alternately clicked to turn the stimulation onor off. The programming screen 100 further includes various stimulationparameter controls that can be operated by the user to manually adjuststimulation parameters. In particular, the programming screen 100includes a pulse width adjustment control 104 (expressed in microseconds(μs)), a pulse rate adjustment control 106 (expressed in pulses persecond (pps), and a pulse amplitude adjustment control 108 (expressed inmilliamperes (mA)). Each control includes a first arrow that can beclicked to decrease the value of the respective stimulation parameterand a second arrow that can be clicked to increase the value of therespective stimulation parameter. The programming screen 100 alsoincludes multipolar/monopolar stimulation selection control 110, whichincludes check boxes that can be alternately clicked by the user toprovide multipolar or monopolar stimulation. In an optional embodiment,the case 40 of the IPG 14 may be treated as one of the lead electrodes26, such that both the case electrode 40 and at least one of the leadelectrodes 26 can be used to convey anodic electrical current at thesame time.

The programming screen 100 also includes an electrode combinationcontrol 112 having arrows that can be clicked by the user to select oneof three different electrode combinations 1-4. Each of the electrodecombinations 1-4 can be created using a variety of control elements.

The user interface includes a mode selection control element 114 and twosets of electrical stimulation field modification control elements—a setof axial modification control elements 116 and a set of circumferentialmodification control elements 118. In the illustrated embodiments, themode selection control element 114 and sets of field modificationcontrol elements 116, 118, as well as the other control elementsdiscussed herein, are implemented as a graphical icon that can beclicked with a mouse or touched with a finger in the case of atouchscreen. Alternatively, the control elements described herein may beimplemented as mechanical buttons, keys, sliders, etc. that can bepressed or otherwise moved to actuate the control elements.

When the mode selection control element 114 is actuated, the processor80 is configured for selectively placing the field modification controlelements in either an electrical stimulation field displacement mode,during which the processor 80 generates stimulation parameter setsdesigned to axially and/or circumferentially displace the locus of theelectrical stimulation field relative to the axis of the lead(s) 12, asdiscussed above with respect to FIGS. 8A-8D, or in an electrical fieldstimulation field shaping mode, during which the processor 80 generatesstimulation parameter sets designed to axially or circumferentiallyexpand/contract electrical stimulation field relative to the axis of thelead(s) 12, as discussed above with respect to FIGS. 9A-9D. The outputtelemetry circuitry 86 is configured for transmitting these stimulationparameters sets to the IPG 14.

In the illustrated embodiment, the mode selection control element 114includes check boxes that can be alternately clicked by the user toselectively place the field modification control elements between theelectrical stimulation field displacement mode and the electricalstimulation field shaping mode. Alternatively, the mode selectioncontrol element 114 takes the form of a button that can be repeatedlyclicked to toggle the field modification control elements 116, 118between the modes.

Each of the sets of field modification control elements 116, 118 takesthe form of a double arrow (i.e., two oppositely pointing controlelement arrows) that can be actuated to modify the electricalstimulation field depending on the mode of operation.

For example, in the field displacement mode, an upper arrow controlelement 116 a of the set of axial modification control elements can beclicked to axially displace the locus of the electrical stimulationfield (i.e., along the axis of the lead(s) 12) in the proximaldirection; a lower arrow control element 116 b of the set of axialmodification control elements can be clicked to axially displace thelocus of the electrical stimulation field (i.e., along the axis of thelead(s) 12) in the distal direction; a left arrow control element 118 aof the set of circumferential control elements can be clicked tocircumferentially displace the locus of the electrical stimulation field(i.e., about the axis of the lead(s) 12) in the counterclockwisedirection; and a right arrow control element 118 b of the set ofcircumferential control elements can be clicked to circumferentiallydisplace the locus of the electrical stimulation field (i.e., about theaxis of the lead(s) 12) in the clockwise direction.

In the field shaping mode, the lower arrow control element 116 a of theset of axial modification control elements can be clicked to axiallycontract the electrical stimulation field about its locus; the upperarrow control element 116 b of the set of axial modification controlelements can be clicked to axially expand the electrical stimulationfield about its locus; the left arrow control element 118 a of the setof circumferential control elements can be clicked to circumferentiallycontract the electrical stimulation field about its locus; and the rightarrow control element 118 b of the set of circumferential controlelements can be clicked to circumferentially expand the electricalstimulation field about its locus.

Thus, it can be appreciated that by virtue of the mode selection controlelement 114, the sets of field modification control elements 116, 118can have a dual-function; i.e., the same control element can be operatedto both displace the locus of the electrical stimulation field and shapethe electrical stimulation field about its locus.

In addition, and particularly with respect to the set of circumferentialmodification control elements 118, the processor 80 generatesstimulation parameter sets designed to circumferentially displace thelocus of the electrical stimulation field about the lead(s) 12 in afirst rotational direction at respective different angular positions asone of the circumferential modification control elements 118 a, 118 b iscontinually actuated; i.e., by continuously actuating one of the controlelements 118 a, 118 b, e.g., by clicking on holding one of the controlelements 118 a, 118 b down, or repeatedly actuating one of the controlelements 118 a, 118 b, e.g., by repeatedly clicking and releasing one ofthe control elements 118 a, 118 b.

Thus, it can be appreciated that the left arrow control element 118 amay be continually actuated, such that the locus of the electricalstimulation field is circumferentially displaced about the lead(s) 12 ina counterclockwise direction at different angular positions, and theright arrow control element 118 b may be continually actuated, such thatthe locus of the electrical stimulation field is circumferentiallydisplaced about the lead(s) 12 in a clockwise direction at differentangular positions.

The user interface of the CP 18 optionally includes a set of radialmodification control elements 120 taking the form of a double arrow(i.e., two oppositely pointing control element arrows). When the set ofradial modification control elements 120 are actuated, the processor 80is configured for generating stimulation parameter sets designed toradially displace the locus of the electrical stimulation field relativeto the axis of the lead(s) 12, as discussed above with respect to FIGS.8B and 8E. In particular, an upper arrow control element 120 a of theset of radial modification control elements can be clicked to radiallydisplace the locus of the electrical stimulation field inward towardsthe axis of the lead(s) 12), and a lower arrow control element 120 b ofthe set of radial modification control elements can be clicked toradially displace the locus of the electrical stimulation field outwardfrom the axis of the lead(s) 12). The output telemetry circuitry 86 isconfigured for transmitting stimulation parameters sets generated by theprocessor 80 to the IPG 14.

Although the indicators of the circumferential modification controlelements 118 a, 118 b respectively take the form of left and rightarrows, other indicators can be used for circumferential modificationcontrol elements dedicated to displacement of the locus of theelectrical stimulation field.

For example, as shown in FIG. 11A, the control element 118 c may beindicated as a counterclockwise circular arrow indicating that the locusof the electrical stimulation field will be circumferentially displacedat different angular positions in the counterclockwise direction whencontinually actuated, and the control element 118 d may be indicated asa clockwise circular arrow indicating that the locus of the electricalstimulation field will be circumferentially displaced at differentangular positions in the clockwise direction when continually actuated.

As shown in FIG. 11B, the control element 118 e may be indicated as adecreasing angle indicating that the locus of the electrical stimulationfield will be circumferentially displaced at different angular positionsin the clockwise direction when continually actuated until the nominalangle of the electrical stimulation field is reduced to 0 degrees, andthe control element 118 f may be indicated as an increasing angleindicating that the locus of the electrical stimulation field will becircumferentially displaced at different angular positions in thecounterclockwise direction when continually actuated until the nominalangle of the electrical stimulation field is increased to 360 degrees.Of note, the indicator on the control element can change when the modeselection is changed. For example, in displacement mode, indicatorsmight be those of FIG. 11A, while in shape mode the indicators might bethose of FIG. 11B.

As shown in FIG. 11C, a control element 118 g may be indicated as anangle indicating that the locus of the electrical stimulation field willbe circumferentially displaced at different angular positions in theclockwise direction when continually actuated. In this case, the angleof the electrical stimulation field wraps around, such that there is nobeginning or ending of the angle.

In an optional embodiment shown in FIG. 12A, the user interface of theCP 18 optionally comprises a rotational control element 122 a capable ofbeing rotated about a point. The processor 80 generates a set ofstimulation parameters designed to circumferentially displace a locus ofthe electrical stimulation field about the lead(s) 12 when therotational control element 122 a is rotated about the point 124, whichset of stimulation parameters is then transmitted from the outputcircuitry 86 of the CP 18 to the IPG 14. In the illustrated embodiment,the rotational control element 122 a is implemented as a graphical icon.In this case, the rotational control element 122 a can simply be clickedon with a cursor (or touched) and dragged to rotate it. Alternatively,the rotational control element 122 a can be a mechanical dial that canbe physically rotated by the user.

The user interface optionally includes a marker 126 associated with therotational control element 122 a for indicating the circumferentialposition of the locus of the electrical stimulation field. In theillustrated embodiment, the marker 126 takes the form of an arrow thatrotates with the rotational control element 122 a. Alternatively, therotational control element takes the form of an arrow 122 b, as shown inFIG. 12B, or an arrow 122 c, as shown in FIG. 12C, in which case, therotational control element 122, itself, provides an indicator of thecircumferential position of the locus of the electrical stimulationfield. In another alternative embodiment shown in FIG. 12D, therotational control element 122 is segmented into pie-shaped sections. Inthis case, the marker 126 takes the form of one or more pie-shapedsections that are highlighted when adjacent a fixed element 126 toindicate the circumferential position of the locus of the electricalstimulation field. As shown in FIG. 12E, the rotational control element122 e takes the form of a segmented ring, with one or more of thesegments highlighted when adjacent a fixed element 126 to indicate thecircumferential position of the locus of the electrical stimulationfield.

Referring back to FIG. 12A, the user interface of the CP 18 optionallyincludes a radial modification control element 128 capable of beingdisplaced along the radius of the rotational control element 122 a. Theprocessor 80 generates a set of stimulation parameters designed toradially displace the locus of the electrical stimulation field when theradial modification control element 128 is actuated, which set ofstimulation parameters is then transmitted from the output circuitry 86of the CP 18 to the IPG 14. In the illustrated embodiment, the radialmodification control element 128 is implemented as a graphical icon. Inthis case, the radial modification control element 128 can simply beclicked on and dragged to radially displace it inward or outward.Radially inward displacement of the radial modification control element128 displaces the locus of the electrical stimulation field radiallyinward towards the point about which the rotational control element 122a rotates, whereas radially outward displacement of the radialmodification control element 128 displaces the locus of the electricalstimulation field radially outward away from the point about which therotational control element 122 a rotates.

Referring back to FIG. 10, programming screen 100 of the CP 18optionally or alternatively displays a three-dimensional graphicalrenderings of the lead 12′ and electrodes 26′ and a plurality of iconiccontrol elements 130 graphically linked to the three-dimensionalelectrode renderings 26′. In the illustrated embodiment, the controlelements 130 are directly linked to the electrode renderings 26′.Alternatively, as shown in FIG. 13, the control elements 130 areindirectly linked to the electrode renderings 26′ via reference lines132. In either case, the processor 80 generates stimulation parametersdesigned to modify the electrical stimulation field when any of thethese control elements 130 is actuated, which stimulation parameters arethen transmitted from the output circuitry 86 of the CP 18 to the IPG14. In the illustrated embodiment, each of the control elements 130 hasan up arrow and a down arrow that can be respectively actuated (e.g., byclicking) to respectively increase or decrease the electrical currentflowing through the electrode 26 corresponding to the graphicalelectrode rendering 26′ to which the actuated control element 126 isgraphically linked. The control element 126 also includes an indicator134 that provides an indication of the amount of electrical currentflowing through each of the electrodes 26 in terms of a fractionalizedcurrent value. The indicators 134 may perform this function when therespective control elements 130 are actuated or when the axialmodification control elements 116, circumferential modification controlelements 118, or radial modification control elements 120 are actuated.

The programming screen 100 of the CP 18 also displays otherthree-dimensional graphical renderings of the lead 12″ and electrodes26″ relative to a graphical anatomical structure 200 that is preferablythe stimulation target. For example, if the DBS indication isParkinson's disease, the anatomical structure 200 is preferably thesubthalamic nucleus (STN) or the globus pallidus (GPi). If the DBSindication is Essential Tremor, the anatomical structure 200 ispreferably the thalamus. If the DBS indication is depression, theanatomical structure 200 is one or more of the nucleus acumbens, ventralstriatum, ventral capsule, anterior capsule, or the Brodmann's area 25.If the DBS indication is epilepsy, the anatomical structure 200 ispreferably the anterior nucleus. If the DBS indication is a gaitdisorder, the anatomical structure 200 is preferably thepedunculopontine (PPN). If the DBS indication is dementia, Alzheimer'sdisease or memory disorders, the anatomical structure 200 is preferablyanywhere in the Papez circuit. The anatomical structure 200 can beobtained from any available brain atlas, or from a patient specificbrain atlas derived from, e.g., a magnetic resonant imager (MRI),computed tomography (CT), X-ray, fluoroscopy, ventriculography,ultrasound, or any other imaging modality or a merging of any or all ofthese modalities.

Based on the current stimulation parameter set, the processor 80estimates a resulting volume of tissue activation (VTA) 202, anddisplays it with the graphical lead 12″ and graphical anatomicalstructure 200. In the preferred embodiment, the VTA 202 is superimposedover the graphical anatomical structure 200. In the illustratedembodiment, although the graphical lead 12″, graphical anatomicalstructure 200, and VTA 202 are displayed in an oblique view, they can bealternatively displayed in any one or more of traditional planes ofsection (e.g., axial, coronal, and sagittal), as shown in FIG. 14. Theuser can specify the general shape of the VTA 202 (e.g., spherical,ovoid, etc.) in any coordinate space desired, e.g., Tailerach,Horsely-Clark, Cartesian, etc. Or the margins of the VTA 202 can beclicked on and dragged to the user's specifications. In an optionalembodiment, the user may thumb through the images in each planesimultaneously or though one plane of section at a time by selecting oneof the check boxes in a view control element 140.

In one embodiment, the user can remove different sections (octants) ofthe brain, for example, the one closest to the viewer in FIG. 14 anddemarcated (outlined) by planes A (axial), B (coronal) and C (sagittal).The user can remove any one or several of these 8 “blocks” of tissue tovisualize the target tissue or VTA 202. The user can then visualize thetarget or VTA 202 projected onto any one, two or all three of the planesof section. The user can move the planes independently to scroll throughsections in each plane. For example, the user could move plane A up anddown independent of the other sections to view the target or VTA 202projection onto different adjacent sections. Similarly, the user couldmove planes B or C independent of the other two planes to visualize thetarget or VTA 202 in adjacent sections. The user can also rotate theentire 3-D structure to view the target or VTA 202 from any angle.

The programming screen 100 further includes a set of axial leaddisplacement control elements 138 and a set of circumferential leaddisplacement control elements 138 that can be actuated to synchronouslydisplace both the graphical lead 12′ with the control elements 130 andthe graphical lead 12″ and associated VTA 202 relative to the graphicalanatomical structure 200.

When the set of axial lead displacement control elements 136 areactuated, the processor 80 is configured for synchronously and axiallydisplacing both the graphical lead 12′ and the graphical lead 12″ andassociated VTA 202 in the same direction by the same distance (i.e.,moving the graphical leads 12′, 12″ and VTA 202 along the respectiveaxes of the graphical leads the same linear distance). In particular, anupper arrow control element 136 a of the set of axial lead displacementcontrol elements can be clicked to axially displace the graphical lead12′ and the graphical lead 12″ and associated VTA 202 relative to theanatomical structure 200 in the proximal direction, and a lower arrowcontrol element 136 b of the set of axial lead displacement controlelements can be clicked to axially displace the graphical lead 12′ andthe graphical lead 12″ and associated VTA 202 relative to the anatomicalstructure 200 in the distal direction.

When the set of circumferential lead displacement control elements 138are actuated, the processor 80 is configured for synchronously andcircumferentially displacing both the graphical lead 12′ and thegraphical lead 12″ and associated VTA 202 in the same direction by thesame distance (i.e., rotating the graphical leads 12′, 12″ and VTA 202about the respective axes of the graphical leads the same angulardistance). In particular, an upper arrow control element 138 a of theset of circumferential lead displacement control elements can be clickedto circumferentially displace the graphical lead 12′ and the graphicallead 12″ and associated VTA 202 relative to the anatomical structure 200in the counterclockwise direction, and a lower arrow control element 138b of the set of circumferential lead displacement control elements canbe clicked to circumferentially displace the graphical lead 12′ and thegraphical lead 12″ and associated VTA 202 relative to the anatomicalstructure 200 in the clockwise direction.

Although the foregoing techniques have been described as beingimplemented in the CP 16, it should be noted that this technique may bealternatively or additionally implemented in the RC 14.

Although particular embodiments of the present inventions have beenshown and described, it will be understood that it is not intended tolimit the present inventions to the preferred embodiments, and it willbe obvious to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe present inventions. Thus, the present inventions are intended tocover alternatives, modifications, and equivalents, which may beincluded within the spirit and scope of the present inventions asdefined by the claims.

What is claimed is:
 1. An external control device for use with aneurostimulation system having one or more neurostimulation leadscarrying a plurality of electrodes capable of conveying an electricalstimulation field into tissue in which the electrodes are implanted,comprising: a user interface including a representation of theelectrodes and a rotational control element configured for beingactuated by rotating the rotational control element about a point; aprocessor configured for generating a set of stimulation parameters torotationally displace a locus of the electrical stimulation field asindicated by the rotational control element by controlling a selectionof one or more electrodes from the plurality of electrodes andcontrolling an adjustable fractionalization of a total amount of currentflowing collectively through the selected one or more electrodes whenthe rotational control element is actuated, wherein thefractionalization describes, for each of the selected one or moreelectrodes, what fraction of the total amount of current flows throughthat electrode; and output circuitry configured for transmitting the setof stimulation parameters to the neurostimulation system.
 2. Theexternal control device of claim 1, wherein the user interface furtherincludes a representation of an estimate of a volume of tissueactivation generated using the set of stimulation parameters and theelectrodes and a first circumferential modification control element anda second circumferential modification control element configured forbeing actuated; wherein the processor is further configured forgenerating stimulation parameters designed to circumferentially contractthe representation of the estimate of the volume of tissue activation inresponse to actuation of the first circumferential modification controlelement and for generating stimulation parameters designed tocircumferentially expand the representation of the estimate of thevolume of tissue activation in response to actuation of the secondcircumferential modification control element.
 3. The external controldevice of claim 2, wherein the user interface further comprises arepresentation of a portion of at least one of the one or moreneurostimulation leads.
 4. The external control device of claim 2, theuser interface further comprises a circumferential stimulationdisplacement control element configured for being actuated, theprocessor is further configured for generating stimulation parametersdesigned to circumferentially displace the representation of theestimate of the volume of tissue activation about the one or moreneurostimulation leads in a rotational direction in response toactuation of the circumferential stimulation displacement controlelement.
 5. The external control device of claim 2, wherein the userinterface further comprises a radial modification control element, theprocessor is further configured for generating stimulation parametersdesigned to radially displace the representation of the estimate of thevolume of tissue activation in response to actuation of the radialmodification control element.
 6. The external control device of claim 2,wherein the user interface further comprises an axial modificationcontrol element, the processor is further configured for generatingstimulation parameters designed to axially displace the representationof the estimate of the volume of tissue activation in response toactuation of the axial modification control element.
 7. The externalcontrol device of claim 2, wherein the user interface further comprisesan axial modification control element, the processor is furtherconfigured for generating stimulation parameters designed to axiallyexpand or contract the representation of the estimate of the volume oftissue activation in response to actuation of the axial modificationcontrol element.
 8. The external control device of claim 2 wherein theuser interface further includes a representation of an anatomicalstructure and the representation of the anatomical structure is dividedinto segments and the processor is configured for removing, in responseto user input, one or more of the segments of the anatomical structureto visualize a target or the estimate of the volume of tissueactivation.
 9. The external control device of claim 8, wherein theanatomical structure is a brain and the brain is demarcated by axial,coronal, and sagittal planes.
 10. The external control device of claim9, wherein the processor is configured for moving, in response to userinput, one or more of the axial, coronal, or sagittal planes.
 11. Theexternal control device of claim 2, wherein the user interface furthercomprises a representation of an anatomical structure, an axial leaddisplacement control element, and a circumferential lead displacementcontrol element, the processor is further configured for generatingstimulation parameters designed to axially displace the representationof the electrodes and the representation of the estimate of the volumeof tissue activation relative to the representation of the anatomicalstructure in response to actuation of the axial lead displacementcontrol element and to circumferentially displace the representation ofthe electrodes and the representation of the estimate of the volume oftissue activation relative to the representation of the anatomicalstructure in response to actuation of the circumferential leaddisplacement control element.
 12. The external control device of claim1, wherein the rotational control element is a mechanical dial that canbe physically rotated by a user.
 13. The external control device ofclaim 1, wherein the rotational control element takes a form of an iconthat can be dragged to rotate it.
 14. The external control device ofclaim 1, wherein the user interface further comprises a markerassociated with the rotational control element for indicating acircumferential position of the locus of the electrical stimulationfield.
 15. The external control device of claim 14, wherein the markertakes a form of a rotatable arrow.
 16. The external control device ofclaim 14, wherein the marker takes a form of a rotatable arrowhead. 17.The external control device of claim 1, wherein the rotational controlelement is segmented into pie-shaped sections Which are selected whenadjacent an element that indicates a circumferential position of thelocus of the electrical stimulation field.
 18. The external controldevice of claim 17, wherein the user interface further comprises amarker associated with the rotational control element for indicating acircumferential position of the locus of the electrical stimulationfield, wherein the marker takes a form of one or more of the pie-shapedsections being highlighted.
 19. The external control device of claim 1,wherein the rotational control element takes a form of a ring ofsegments which are selected when adjacent an element that indicates acircumferential position of the locus of the electrical stimulationfield.
 20. The external control device of claim 19, wherein the userinterface further comprises a marker associated with the rotationalcontrol element for indicating a circumferential position of the locusof the electrical stimulation field, wherein the marker takes a form ofone or more of the segments being highlighted.